From EP 1 331 037 A2 a rotation atomiser is known which discharges a spray jet of a coating agent by means of a rotating bell. For the purpose of shaping the spray jet discharged from the bell, this rotation atomiser has a plurality of guide air nozzles which are arranged in two concentric rings around the bell and which discharge a guide air stream (shaping air) from the rear in an essentially axial direction onto the spray jet, through which the spray jet width can be adjusted.
For an internal painting, a small spray jet width is adjusted due to the restricted space conditions where, by way of the guide air nozzles, a large guide air flow is discharged which presses the spray jet together from the outside.
For an external painting, however, a wide spray jet is preferably adjusted in order to enable the painting of large component surfaces in a quick and efficient manner. For this purpose, a small guide air flow is discharged at the very most, so that the spray jet is pressed together to a small extent only.
Therefore, with the known rotation atomiser various values are adjusted for the guide air flow in order to optionally obtain a narrow spray jet or a wide spray jet.
The disadvantage with the method for adjusting the guide air flow as described above is the fact that the correlation between a certain guide air flow and the resulting spray jet width in the operation of the rotation atomiser is subject to variations and this makes an exact adjustment of the spray jet width difficult.
From U.S. Pat. No. 6,534,127 B2 a guide air control is known where the temperature and the humidity of the discharged guide air are controlled. In this case, however, the spray jet width is also dependent on the current operating conditions of the rotation atomiser because the correlation between the guide air volume flow and the resulting spray jet width fluctuates depending on the current operating conditions.
From US 2002/0122892 A1 a guide air control is known where the speed of the guide air flow is influenced in order to keep a so-called control relationship constant, wherein the matter involved is the relationship between the product of rotational speed and guide air volume on the one hand and the coating agent volume flow on the other. In this case, therefore, the control pursues a different control objective and does not prevent a variation of the spray jet width depending on the current operating conditions.
Finally, DE 199 38 093 A1 discloses a control system which controls the guide air volume flow as a control variable to a pre-specified set value, wherein the set value can be varied according to the desired spray jet width. In this case, however, the problem occurs in that the correlation between the guide air volume flow and the resulting spray jet width fluctuates depending on the current operating conditions of the rotation atomiser.
Therefore, the object underlying the invention is to improve the known rotation atomiser as described above and the operating method related to it.
This object is achieved by the exemplary operating methods and coating apparatuses, respectively, disclosed herein.